I just found an old blue Clay Magic bar in the cupboard that had been there for a decade or two. I used it to clay an older truck last Friday. It worked great and held together great, but when I got done, I looked like I had murdered a Smurf. Took a day or so before the blue die came out of my hands.
Haven't used the synthetic clay mitts or bonnets yet, I have about a lifetime's worth of Mother's and Griot's Garage clay left over, so I'll probably never get to it. As was mentioned above, clay is clay, with the exception you should look for the fine stuff, and don't get the more abrasive kind like the red Clay Magic unless you want to polish out a lot of fine scratches after claying.
I've had good luck with Mother's. I echo the recommendation to use car wash soap at a high concentrate mixed with water in a sprayer. I had a lot of Chemical Guys clay lube on hand, so I used about 25 ounces of that and it worked great. Whatever lube you use, put on way too much, then spray it again. It will help you to not drop the clay bar, after which you have to throw it away if it hits the ground.